$\text{a)}{\left({11}^3\right)}^4:{\left({11}^2\right)}^5={11}^{3\cdot 4}:{11}^{2\cdot 5}={11}^{12}:{11}^{10}=$  

$={11}^{12-10}={11}^2=11\cdot 11=121$  

$\text{b)}\frac{2^2\cdot 2^{10}}{{\left(2^3\right)}^5}=\frac{2^{2+10}}{2^{3\cdot 5}}=\frac{2^{12}}{2^{15}}=\frac{2^{12}}{2^{12}\cdot 2^3}=\frac{{\sout{2^{12}}}^1}{{\sout{2^{12}}}^1\cdot 2^3}=\frac{1}{1\cdot 2^3}=\frac{1}{8}$